Răspuns:
este normal dar un pic greu
Explicație pas cu pas:
a) 933+(455+148)=933+603=1536
1187+(870-230)=1187+640=1827
7500-(1250+1250)=7500-2500=5000
b) 2845-829+2400=2016+2400=4416
15780-(1075+2750)=15780-3825=11955
6204+(3000-2200)=6204+800=7000
7911 - [8 211-(10 100 - 5702)]=7911-[8211-4498]=
=7911-3713=4198
12 563 - [1 456 + (9 876-867)]=12536-[1456+9001]=
=12536-10457=12079
7 015 - [3 015 - (2004 - 4)]=7015-[3015-2000]=
=7015-1015=6000